Abstract: A high frequency ventilator which generates a high frequency pressure wave in a supply of ventilating gas for supporting ventilation in air breathing animals. The high frequency pressure wave causes the ventilating gas to be exchanged and to diffuse through the animal's lungs fast enough to support ventilation without spontaneous breathing on the part of the animal and without the aid of a separate ventilator.

Abstract: A high frequency oscillating ventilator. A flow of gas is conducted from a gas source to a high frequency oscillator. The high frequency oscillator comprises a housing including a magnet and having a diaphragmetically sealed piston mounted therein, an inlet connecting the space within the housing on the first side of the diaphragm to the gas conducting means, and a coil mounted to the first side of the diaphragm. Circuitry is provided which is operable to reverse the polarity of the flow of the current in the coil, thereby causing the diaphragm to move back and forth within the housing. A tube connecting the space on the second side of the diaphragm to the gas source and the patient's airway is provided. Also disclosed is a method of ventilating a patient with the high frequency oscillating ventilator, and a double lumen endotracheal tube for use in connection therewith.

Abstract: A temperature control system for an electrically heated cutaneous gas sensor. A heating element is provided with heating current by a closed loop temperature control circuit. The system includes a plurality of temperature monitoring circuits which are arranged to turn off the flow of heating current if the temperature of the sensor takes on an unacceptable value. The system also includes temperature setting circuitry for applying an increased temperature setpoint signal to the temperature control circuit, for a predetermined time, to reduce the time delay between the application of the sensor to the patient and the production of usable sensor data. Timing circuitry assures that the flow of heating current is not turned off in response to normal sensor temperature transients.

Abstract: An improved method and apparatus for deplating the electrodes of cutaneous oxygen sensors. A controllable voltage source selectably establishes either a polarizing voltage or a deplating voltage between the electrodes of a cutaneous oxygen sensor, while a current sensing circuit measures the current flow therebetween. If, during the calibration of the sensor, the current flow exceeds a predetermined threshold, the apparatus initiates an operator assisted sequence of operations which deplate the electrodes and restore the gas sensor to a usable operating condition. During the performance of this sequence of operations, the apparatus carries out all steps, except those which must be performed manually by an operator.

Abstract: An improved device for determining the trend of the partial pressure of a gas, such as oxygen or carbon dioxide, which diffuses outwardly through a patient's skin. The device, such as a cutaneous gas monitor, generates over time a series of partial pressure input values that are compared to one another for determining a trend in the partial pressure. This trend is communicated to the operator of the device.

Abstract: A temperature control system for an electrically heated cutaneous gas sensor. A closed loop temperature control circuit varies the current through the heating element, in accordance with the sensed temperature of the sensor, to maintain the sensor at a temperature approximately equal to that set by a temperature setpoint signal. As the sensor is first placed on a patient, the magnitude of the temperature setpoint signal is increased above its normal value, for a predetermined time, in order to decrease the time delay between the time that the sensor is placed on the patient and the time that the sensor begins to provide usable data.

Abstract: A temperature control system for an electrically heated cutaneous gas sensor. A heating element is provided with heating current by a closed loop temperature control system. The system includes a plurality of temperature monitoring and control circuits which are arranged to turn off a switch that controls the flow of current through the heating element if the temperature of the sensor varies outside of acceptable limits. The system also includes latching circuitry for maintaining the off state of the switch after the occurrence of an out of limits condition, and circuitry for preventing the latching circuitry from being actuated during normal temperature transients.

Abstract: A method for calibrating and linearizing the output of an instrument that includes a transducer having an output that is a nonlinear function of a property of interest of a fluid. The results of measurements performed on a plurality of transducers of the type to be used in the instrument are used to produce first and second equations which give the direct and inverse responses of a typical transducer. The results of further measurements on the particular transducer to be used in the instrument are used with the first equation to define how the second equation may be used to give accurate results with the particular transducer. The instrument is then calibrated and the results used with the second equation to produce an accurate linearized value for display as the output of the instrument.

Abstract: An improved switching device for indicating the beginning and ending of the breath of a test subject. A flow through housing is provided with an inlet and first and second outlets. A flexible diaphragm is connected in series with the first outlet to serve as a check valve which opens during the high flow rate portion of a breath. A sensitive flow responsive member connected in series with the second outlet opens in response to the presence of gas flow during the low flow rate portion of the breath. A detecting circuit responsive to the position of the flow responsive member accurately signals the beginning and ending of a breath without interference by the check valve.

Abstract: A calibration syringe for controllably delivering gas to a respiratory gas measuring instrument during the calibration thereof. In addition to the piston and cylinder arrangement used in prior syringes, the calibration syringe of the invention includes several improvements which enhance the accuracy and repeatability of the volume of gas delivered thereby. One improvement comprises a modified inlet-outlet design which assures a positive shutoff of the flow of gas at the end of an ejection stroke. A second improvement comprises the provision of a spring-loaded mechanism for automatically propelling the piston at any of several operator selectable rates. Finally, the calibration syringe of the invention includes a latching arrangement which assures that each ejection stroke begins from the same starting position and is initiated in a way that minimizes operator-related effects.

Abstract: An improved switching device for indicating the beginning and ending of the breath of a test subject. A flow through housing is provided with an inlet and first and second outlets. A flexible diaphragm is connected in series with the first outlet to serve as a check valve which opens during the high flow rate portion of a breath. A sensitive flow responsive member connected in series with the second outlet opens in response to the presence of gas flow during the low flow rate portion of the breath. A detecting circuit responsive to the position of the flow responsive member accurately signals the beginning and ending of a breath. A damping member connected to the flexible diaphragm prevents the latter from vibrating at low breath flow rates and thereby stabilizes the motion of the flow responsive member.

Abstract: An improved gas volume calibration method and apparatus for use in respiratory gas analyzers. A control unit monitors the flow of calibration gas through the analyzer by monitoring the electrical signals produced by a gas turbine and a breath switch. During calibration, a known volume of calibration gas is repeatedly delivered to the analyzer from a calibration syringe at each of a number of different flow rates. On the basis of the information received from the turbine and the breath switch, the control unit generates and stores a piecewise linear approximation of the nonlinear characteristic of the turbine. This stored turbine characteristic is then made available during subsequent measurements to eliminate those volume errors which are associated with variations in the rate at which the sample gas is delivered, thereby affording measurements of improved accuracy.